Hi, i have a time domine plot (displacement vs time). i want to convert to frequency domine plot (amplitude vs frequency).

Hi, i have a time domine plot (displacement vs time). i want to convert to frequency domine plot (amplitude vs frequency).

Answer 1

[Julian Sowa]

Hello I have done this a bunch of time with the FFT function. I follow this tutorial and just use the example code they give: https://www.mathworks.com/help/matlab/ref/fft.html

Here is the example: Just replace the first 5 lines with your paramaters! LMK if it works for you.

Fs = 1000; % Sampling frequency

T = 1/Fs; % Sampling period

L = 1500; % Length of signal

t = (0:L-1)*T; % Time vector

X = 0.7*sin(2*pi*50*t) + sin(2*pi*120*t); % Replace this with the array of your displacement samples

plot(1000*t(1:50),X(1:50))

title('Time Domain')

xlabel('t (milliseconds)')

ylabel('X(t)')

Y = fft(X);

P2 = abs(Y/L);

P1 = P2(1:L/2+1);

P1(2:end-1) = 2*P1(2:end-1);

f = Fs*(0:(L/2))/L;

figure

plot(f,P1)

title('Single-Sided Amplitude Spectrum of X(t) (Frequency Domain)')

xlabel('f (Hz)')

ylabel('|P1(f)|')